Pipe testing apparatus

ABSTRACT

A pipe testing apparatus comprising an elongate tester body having sealing means and actuator means to deform said sealing means on activation. The apparatus is further provided with means to bias actuator means axially away from the sealing means on deactivation of said actuator means. The apparatus is typically used to test the integrity of pipelines at specific points, for example joints or welds.

PIPE TESTING APPARATUS

This invention relates to apparatus especially, but not exclusively foruse in pipe testing and more particularly pressure testing of pipelinewelds.

Pipelines to the type used to carry oil and gas often travel longdistances and are subject to many potentially damaging effects bothexternally, from environmental effects, and internally, from substantialpressure effects. Clearly the nature of the transported material is suchthat leaks are not acceptable. There is thus a need to carry out testingof the integrity of the pipeline at certain points particularly joins orwelded repair joints. This requires the use of appropriate pressuretesting apparatus.

The pressure testing apparatus used is required to seal off the sectionof pipeline containing the join or weld to be tested so that pressuremay be applied to that area.

The nature of the pipeline is such that any such pressure testingapparatus must be able to deal with two particular difficulties. Theseare the tendency of long lengths of pipeline to acquire a degree ofovality and the corrosive effect of the oil or gas on the internalsurface of the pipeline which can become rough and pitted.

Previously proposed testing apparatus has attempted to overcome thesedifficulties by using resilient material seals which are forced into thegap between the exterior of a testing device and the interior surface ofthe pipeline to take up any ovality or surface imperfections.

A known problem of such an approach is that the seal in being forcedinto the gap between the body of the testing device and the pipeline,and additionally acted upon by the high pressure of the testing maybecome damaged. As a result the testing device requires frequentmaintenance and repair.

A solution to this problem is proposed in GB2242530 where a sealingelement is proposed which as outer and inner portions of varying degreesof resilience and deformability. The outer section is relatively soft,so as to deform to the contours of the pipeline, but the inner sectionis harder so that the overall deformability of the seal is limited. Theseal is pushed against a cam slope by a thrust member acting axially sothat the seal is deformed radially.

While this development goes some way to overcoming the previouslyidentified difficulties it has limitations of its own. The limiteddeformability of the two part seal effectively places very narrow limitson the working diameter of the apparatus. The manner in which the sealis thrust against a cam surface to deform its surface against the pipecan lead to it becoming effectively stuck in position when the axialforce of the thrust member is removed.

It is an object of the present invention to provide pressure testingapparatus which addresses these identified difficulties.

According to the present invention there is provided pipe testingapparatus comprising an elongate tester body having resilientlydeformable pipe sealing means at an end portion thereof and actuatormeans arranged to resiliently deform said sealing means radiallyoutwardly on activation thereof characterised in that an outwardlyangled thrust face on said actuator engages a co-operating inwardlyangled thrust face on said seal means in operation and furthercharacterised in that further resilient means are provided to bias saidactuator axially away from said seal means on deactivation of saidactuator means.

Preferably said sealing means is composed of a nitrile rubber compound.

Most preferably said nitrile rubber compound has a shore hardness in therange of 60 to 90.

Preferably also said actuation means is a hydraulically operated pistonassembly.

Preferably also the thrust faces on said actuator means and said sealmeans are arranged at 45° to the longitudinal axis thereof.

Preferably also the further resilient means is a rubber spring.

Alternatively the further resilient means may be a coil spring.

Preferably also said further resilient means acts between said actuatormeans and said seal means to bias them apart.

Preferably also a pair of said pipe sealing means are provided at eitherend of said tester body to form a pressure testing area.

Preferably means are provided for applying hydraulic pressure to saidpressure testing area.

Embodiments of the present invention will now be described by way ofexample with reference to the accompanying drawings in which:

FIG. 1 is a part cut away side view of a first embodiment of pipetesting apparatus in accordance with the present invention; and

FIG. 2 is a detail view of an alternative sealing member of a secondembodiment of pipe testing apparatus in accordance with the presentinvention.

Referring to FIG. 1 of the drawings, pipe testing apparatus 1 comprisesa tester body 2 which has sealing devices 3 positioned at opposing ends.Each sealing device 3 has a hydraulically operated actuator piston 4which has a thrust surface 5 at one end set at an angle of 45° to thelongitudinal axis of the apparatus. A secondary thrust surface 6 on theend of the piston is not angled. A seal carrier 7 is mounted on each endof the tester body 2 and forms a recess in which a seal 8 and spring 9are mounted. Internal channels 10 and 11 provide a means for applyinghydraulic pressure to the actuator pistons 4 and tester body 2respectively.

The tester body 2 and seal carrier 7 are constructed from high tensilesteel and the actuator pistons 4 from low carbon steel. The seal 8 iscomposed of a nitrile rubber compound having a typical shore hardness inthe range 60 to 90. The spring 9 is composed of rubber.

In use the testing apparatus is inserted in a pipeline and positioned atthe area to be tested. Hydraulic pressure applied through channel 10acts on the piston 4 which are axially displaced so that the thrustsurface 5 acts on a corresponding surface 12 on the seals 8 thus causingthe seals to be displaced radially outwardly to engage the internalsurface of the pipeline and form a pressure tight seal. At the same timethe spring 9 is caused to be compressed by the secondary thrust surface6 acting axially against it.

Pressure testing of the pipeline can then be carried out using thechannel 11 which forms a test pressure port. The seals 8 are able towithstand pressure of several thousand psi.

The movement of the seal 8 is generally radially outward by the combinedinteraction with the thrust surface 5 and seal carrier 7. As a resultthe seal has less tendency to be squeezed into the small gap which mayexist between the exterior of the piston 4 and seal carrier 7 and theinterior of the pipeline which can result in damage to the seal.

When the pressure test is completed the hydraulic pressure on thepistons 4 is released with the result that the pistons 4 are encouragedback towards their original resting position by the compressed spring 9which acts between the pistons 4 and the seals 8. The seals 8 are thusno longer constrained by the thrust surface 5 and have nothing actingupon them to retain them against the pipeline interior. The testingapparatus can thus be easily moved to a new testing area or if requiredremoved from the pipeline.

Various modifications and improvements to the basic apparatus areenvisaged. For example FIG. 2 shows an alternative seal arrangement. Inthis embodiment the seal carrier 7 has a surface 13 complimentary to thethrust surface 5 on the piston 4. The seal 8 also has a second angledend 14 complimentary to the first surface 12. In use the seal iseffectively pushed outwardly by the closing of the gap between thethrust surfaces 5 and 13. Other aspects of the operation of theapparatus are generally as before.

Other modifications anticipated include the substitution of the rubberspring 9 with an alternative spring means such as a coil spring. Theseals 8 may also be composed of other materials having similar physicalcharacteristics to the nitrile rubber compound. The basic constructiontogether with the suggested variations allow the apparatus to operateeffectively over a range of diameters.

Further modifications and improvements may be incorporated withoutdeparting from the scope of the invention herein intended.

What is claimed is:
 1. Pipe testing apparatus comprising an elongatetester body on a longitudinal axis having resiliently deformable pipesealing means at an end portion thereof and actuator means arranged todeform said sealing means radially outwardly on activation thereof,characterised in that said sealing means has a first thrust faceinwardly angled from the longitudinal axis and an oppositely arrangedsecond thrust face perpendicular to the longitudinal axis, said actuatorhas a co-operating actuating thrust face outwardly angled from thelongitudinal axis to engage the first thrust face on said sealing meansin operation, said apparatus including a seal carrier having a carrierthrust face perpendicular to the longitudinal axis, wherein the carrierthrust face engages the second thrust face on said sealing means suchthat the sealing means resiliently deforms by the combined interactionof the actuator thrust face and the carrier thrust face on activation ofthe actuator means, the actuator means is a hydraulically operatedpiston assembly and further resilient means are provided to bias saidactuator axially away from said sealing means on deactivation of saidactuator means.
 2. Pipe testing apparatus as claimed in claim 1 whereinsaid sealing means is composed of a nitrile rubber compound.
 3. Pipetesting apparatus as claimed in claim 2 wherein said nitrile rubbercompound has a shore hardness in the range of 60 to
 90. 4. Pipe testingapparatus as claimed in claim 1 wherein the actuator thrust face on saidactuator means and the first thrust face on said sealing means arearranged at 45° to the longitudinal axis thereof.
 5. Pipe testingapparatus as claimed in claim 1 wherein the further resilient means is arubber spring.
 6. Pipe testing apparatus as claimed in claim 1 whereinsaid further resilient means acts between said actuator means and saidseal means to bias them apart.
 7. Pipe testing apparatus as claimed inclaim 1 wherein a pair of said pipe sealing means are provided at eitherend of said tester body to form a pressure testing area.
 8. Pipe testingapparatus as claimed in claim 1 wherein means are provided for applyinghydraulic pressure to said pressure testing area.